For example, in a chair which is used in an office or the like, there is a chair in which a seat surface height can be adjusted or strength of locking can be adjusted. An operation member for performing the adjustments is provided in this chair, and for example, a seated person can perform various adjustments by changing a posture of the operation member (for example, refer to Patent Document 1).
Meanwhile, for example, Patent Document 2 discloses a load support member for a chair in which an extension material having an elastic resistance force (repulsive force) with respect to a load in a surface perpendicular direction is supported by a frame member which is a strength member, and a chair having the load support member for a chair. In the chair disclosed in Patent Document 2, high tension in an up-down direction is secured by a group of warps configuring a structure of the extension material, and a stretching force in a right-left direction is secured by a group of wefts configured of chenille yarn and elastic yarn.
The chair disclosed in Patent Document 2 has a satisfactory seating feeling in which an appropriate elastic resistance and expansion and contraction are compatible. On the other hand, since a group of warps is indispensable in order to maintain a minimum strength and wefts extending in the right-left direction are added to obtain the stretching force, it tends to be a design in which a large number of dot-shaped gaps are formed between the warps and the wefts due to the extensions, and even though the warps and wefts are members which effect the appearance, the degree of freedom in terms of design is likely to decrease.
In order to solve the problems, a configuration disclosed in Patent Document 3 is considered. In a chair disclosed in Patent Document 3, two grooves having directions different from each other are formed in a rod member, extension materials different from each other are fastened to the respective grooves, and a plurality of extension materials extend in a frame member.
According to this configuration, for example, an irregular design in which an element having strong tension is adopted as a rear surface side extension material and an element having weak tension is adopted as a front surface side extension material is possible, and the degree of freedom in terms of design increases.